1. Field of the Invention
The present invention relates to an illuminated keyboard, and in particular to an illuminated keyboard having a light guiding plate.
2. Description of Related Art
There has been a trend toward equipping computers with illuminated keyboards in recent years. We can type easily in a lower light or dark environment because the light guiding plate (LGP) and light source technology has been increasingly employed in computer keyboards.
A conventional illuminated keyboard typically comprises a key switch, a backlight device, a seat, and a light guiding plate. Some conventional illuminated keyboards have complicated structures, such as multi-layer light guiding structure comprising a plurality of LGPs. For example, U.S. Pat. No. 6,860,612 contemplates an illuminated keyboard having an LGP and a light source located on the bottom of the keyboard. The light from the light source has to be transmitted through many layers to reach the keycaps at the top. As a result, manufacture of the illuminated keyboard with such a structure is complicated, and the light emitting capability and efficiency of the illuminated keyboard is limited. Also, please refer to FIG. 1 showing a cross-sectional schematic view of U.S. Pat. No. 6,284,988, the illuminated keyboard of which uses a single Electroluminescent(EL) sheet. The conventional illuminated keyboard, as shown in FIG. 1, roughly comprises a keyboard portion 21, a backlight device 25. The keyboard portion 21 includes a seat 23 and a membrane circuit board 24. The membrane circuit board 24 is provided with an elastic member 26, keycaps 22, and scissors structures 27. As shown in FIG. 1, the illuminated keyboard which employs EL as a backlight device 25 has a reduced the whole thickness of the keyboard. However, using EL as a backlight device has many disadvantages, such as a larger starting voltage, a short life time, complicated circuit designs, decreasing brightness, EMI caused to the membrane circuit board of the keyboard.
To address the aforementioned problems as well as provide various advantages, the present invention is directed to an illuminated keyboard.